Speaker System Design Guide for Yamaha Sound System Simulator Direct and Reflected: Understanding the Truth with Y-S3 -Speaker System Design Guide- December 2008 © 2008 Yamaha Corporation 1
Speaker System Design Guide for Yamaha Sound System Simulator Introduction Y-S3 is a speaker system design software application. It is especially useful in determining speaker placement. The user can easily enter the desired venue shape and calculate the three-dimensional coverage area for given speaker placements and angles.
Speaker System Design Guide for Yamaha Sound System Simulator 1. Setting the speaker arrangement Y-S3 can produce contour diagrams for each speaker array or for each speaker within a speaker array. This allows the user to adjust the speaker arrangement while checking the floor-level coverage area. If the areas covered by individual speakers overlap significantly, sections of phase interference appear over a wide area and cause reinforcements (peaks) and cancellations (dips)*.
Speaker System Design Guide for Yamaha Sound System Simulator ¾ Viewing the coverage area The next step is to check whether the coverage area of the speakers is appropriate. In Y-S3, the user can click to switch into Array Mode and view a contour diagram for the entire array. The figure below shows the results for a splay angle of 50.0.
Speaker System Design Guide for Yamaha Sound System Simulator 250 Hz 500 Hz 1 kHz 2 kHz Figure 2: Sound pressure distributions for different frequency bands (all 1/1 OCT Band; the listed frequency is the center frequency) ; Comparison with Actual Measurements In the actual sound field, the areas of phase interference between speakers will be affected by reflected sounds.
Speaker System Design Guide for Yamaha Sound System Simulator configured appropriately, similar phase interferences between speakers will appear in both the computed and measured results in the middle frequency bands. Therefore, it can be concluded that using the computed results of direct sound only to reduce areas of phase interference will have beneficial effects on the actual sound field.
Speaker System Design Guide for Yamaha Sound System Simulator phase interference are indicated between speakers because the wavelengths of the frequencies in question are relatively long compared to the distance between the speakers. However, areas of phase interference do appear in the measured results on the right side of each figure. These areas are most likely formed through interference between direct sound from the speakers and initial reflections from the walls.
Speaker System Design Guide for Yamaha Sound System Simulator 2. Evaluating the Response at Specific Points The effects of interference between multiple speakers are manifested in the response at a specific point through dips in frequency characteristics. In the actual sound field, it is expected that the depth of the dips will be reduced by reflected sound.
Speaker System Design Guide for Yamaha Sound System Simulator [dB] 0 -10 -20 100 1000 10000 [Hz] Figure 5: Measured and computed results at X = 6, Y = 6 3 Blue: Y-S . Red: Measured results integrated over 15 ms. Pink: Measured results integrated over 100 ms. (The measured results are moving averages.) ¾ Evaluation of High-Frequency Drop-Off Figure 6 shows the computed and measured results at point B (x = 1 m, y = 10 m). Point B is approximately in the center of the seating area.
Speaker System Design Guide for Yamaha Sound System Simulator measurement for point A was made in the seats while the measurement for point B was made in the walkway. The above example shows that the frequency responses at specific points computed using Y-S3 are similar to those that appear in actual sound fields. Understanding this during the design phase will facilitate better measurements and adjustments after the speakers have been arranged.
Speaker System Design Guide for Yamaha Sound System Simulator 3. Configuring Output Levels You can use Y-S3 to estimate the sound pressure levels at different points for different amp types, gains, and input levels. The computed levels can be used to determine whether the system you are designing can obtain the sound pressure levels that you want.
Speaker System Design Guide for Yamaha Sound System Simulator For example, to change the SPL to approximately 100 dB, you could set the amp attenuator level to -6dB and set the input level to 10 dBu. Doing so would change the overall SPL to 100.7 dB. Figure 8: Adjusted level settings ¾ Given the settings shown above, the SPL at a distant point, X = 0, Y = 22.0 for example, would be 95.4 dB. However, in an actual sound field, the level will not decrease that much due to the effects of reflected sound.
Speaker System Design Guide for Yamaha Sound System Simulator directly, and the sound pressure levels rise as a result of the speaker directivity. The measured results for 2 kHz stop attenuating after 13 m, just like the results for 1 kHz. Also, the effects of speaker directivity on the levels are hidden by the effects of the reflected sound.
Speaker System Design Guide for Yamaha Sound System Simulator Figure 10: Theoretical attenuation levels of direct and reflected sounds based on revised formula by Barron (M.
